ABSTRACT

Objectives: To determine the possible association between single umbilical artery (SUA) in the second trimester of pregnancy and the incidence of chromosomal abnormalities. To determine whether the presence of chromosomal defects in fetuses with SUA is related to the side of the missing artery.

Methods: Color flow imaging of the fetal pelvis was used to determine the number of umbilical arteries in 2147 fetuses immediately before amniocentesis for karyotyping in the second trimester of pregnancy.

Results: Single umbilical artery (SUA) was diagnosed in 83/2019 (4.1%) chromosomally normal fetuses, in 5/39 ( 12.8%) with trisomy 21, 8/16 (50%) with trisomy 18, 1/4 (25%) with trisomy 13 and 5/69 (7.2%) with other chromosomal defects. The left umbilical artery was absent in 60/102 (58.8%) fetuses, compared with 42/102 (41,2%) for the right artery. Chromosomal abnormalities occured in 19/102 (18.6%) fetuses (p<0.0001; OR 4.07; 95% CI 2.3-7.1), with 11/60 (18.3%) (p<0.0001; OR 3.99; 95% CI 1.9-8.2) in those with absence of the left artery and 8/42 (19.0%) (p<0.0001; OR 4.18; 95% CI 1.74-9.7) in those with absence of the right artery. Associated structural abnormalities occured in 25/102 (24.5%) fetuses, with 14/60 (23.3%) in those with absence of the left artery and 11/42 (26.2%) in those with absence of the right artery. There were no chromosomal abnormalities in fetuses where a single umbilical artery was an isolated finding. All fetuses with chromosomal abnormalities had associated malformations, 19/19 (100%).

Conclusion: A single umbilical artery (SUA) in the second trimester of pregnancy has a high association with trisomy 18, 13, 21 and other chromosomal defects, but all chromosomally abnormal fetuses had associated malformations detected by ultrasound. The absence of the left artery is more frequent than the absence of the right artery. The association with chromosomal abnormalities seems to be equal on each side.

Key words: single umbilical artery, prenatal diagnosis, second trimester, chromosomal defect, ultrasonography